Unprecedented μ-1,2-bis(monodentate) coordination mode of croconate dianion (C5O52−): Synthesis and crystal structures of manganese- and copper-based coordination polymers

Abstract

Two new coordination polymers {[Mn2(BPP)2(C5O5)2(OH2)4]·3H2O}n (1) and {[Cu4(BPP)4(C5O5)4]·8H2O}n (2) [BPP=1,3-bis(4-pyridyl)propane and C5O52−=croconate anion] were synthesized and characterized by thermal analysis, vibrational spectroscopy (Raman and infrared) and single crystal X-ray diffraction analysis. Compound 1 was obtained under solvothermal conditions and 2 by the diffusion method. Structure determination by single crystal X-ray diffraction analysis revealed that compound 1 presents two-dimensional polymeric nature due to the bridging coordination mode of both BPP ligand and croconate anion. In this case, the croconate anion acts in the unprecedented μ-1,2-bis(monodentate) coordination mode, forming interpenetrated grids of 63 topology. On the other hand, compound 2 is a three-dimensional 4-connected uninodal net of (42·84) topology, due to the presence of the flexible BPP ligand that bridges two Cu(II) sites connecting perpendicular one-dimensional polymeric chains, formed by croconate anions coordinated to the metal centers in a bis-bidentate coordination mode.